In the construction of door closures for the heavy service encountered in large cargo containers, closed bodies for heavy trucks, semi-trailers and the like, where swinging doors are employed, as is commonly desirable at the rear ends of such bodies and containers, it is important that the mechanisms for securing and releasing the doors be of extremely rugged and reliable construction, operable in minimum time and with minimum difficulty under severe and abnormal conditions which arise in such service due to factors such as distortion, or sagging of one of the doors, the presence of ice, dirt and the like in the mechanism, etc. A successful fastening system employed with paired-hinged doors utilized upon heavy containers and bodies of the indicated character, comprises a vertical lock rod on each door near the free edge and projecting above and below the door to overlie the header and sill, each projecting end of the rod carrying fast thereon a hooked finger-like cam which when the rod is rotated by an actuating handle is swingable into and out of overengaged relation with respect to a keeper abutment in a keeper box on the header or sill to pull the door to and secure it in or release it from the fully-closed position. The keeper box is a rugged casting having a relatively narrow opening and the cam, which is somewhat narrower than the keeper box, is tapered to reduced thickness toward its ends in its dimension parallel to its axis of swinging movement. If the door has sagged or become misaligned, but the misalignment is not so great as to eliminate all overlap between the free end of the cam and the opening in the box, the cam, as it is forced into the keeper box, bears against the top or bottom wall of the box and exerts a camming force tending to urge the door into proper alignment with the door opening. Practical considerations including cost and available space militate against the use of anti-friction bearings or ground and polished surfaces on the interengaging parts. Lubricants must also be avoided because of the fact that they become fouled with dust and dirt. Under some conditions when it is necessary to force the cams into the receptacles with great force in order to correct a misaligned condition, it has been difficult to overcome the friction. If the operator exerts great force on the operating handle, as by applying a long pipe as a lever, or otherwise overstressing the parts, damage may be caused to the lock mechanism, despite the construction thereof of heavy steel parts in the most rugged manner feasible.
A primary object of the present invention, therefore, is to provide an improved construction of the indicated character which in a very simple and inexpensive manner overcomes the difficulty indicated, greatly reduces the friction caused by misalignment of the parts, and enables moving the cams into and out of the keeper receptacles easily under virtually all conditions encountered in service.
Other objects and advantages will become apparent upon consideration of the present disclosure in its entirety.